This case study examines the motivational structure of a group of male students (n = 10) in a grade 11 General Science class at an independent single-sex school. We approach the concept of motivation through the integration of three different theoretical approaches: sociocultural theory, future time perspective and achievement goal theory. This framework allows us to stress the dialectical interdependence of motivation, as expressed through individual goals, and the socially and culturally influenced origins of these goals. Our results suggest that the boys internalised the administrative description of the course as meeting a diploma requirement, which they expressed in their perception of the course as being for "non-science" people who "just need a credit." However, we also found situational changes in students' motivational structure towards more intrinsic orientations when they were engaged in topics with personal everyday and future relevance. These situational changes in students' goal structures illustrate that our participants did not internalise classroom and school goal messages wholly and, instead, selectively and constructively transformed these goal messages depending on their own motivational structure and beliefs. These results stress the importance of teachers scaffolding not only for conceptual learning but also for student motivation in science classes, especially those that purposefully teach towards scientific literacy.